vslSkipAheadStreamEx

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

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ID 766686

Date 4/28/2026

Version

Public

vslSkipAheadStreamEx

Initializes a stream using the block-splitting method with partitioned number of skipped elements.

Syntax

status = vslskipAheadstreamEx ( stream , n , nskip )

Include Files

mkl.fi , mkl_vsl.f90

Input Parameters

Name	Type	Description
`stream`	TYPE(VSL_STREAM_STATE) , INTENT(IN)	Pointer to the stream state structure to which block-splitting method is applied
`n`	INTEGER , INTENT(IN)	Number of summands in `nskip`
`nskip`	INTEGER(KIND=8) , INTENT(IN)	Partitioned number of skipped elements

Description

vslSkipAheadStreamEx The vslSkipAheadStreamEx function skips a given number of elements in a random stream. This feature is particularly useful in distributing random numbers from original random stream across different computational nodes. If the largest number of random numbers used by a computational node is nskip , then the original random sequence may be split by vslSkipAheadStreamEx into non-overlapping blocks of nskip size so that each block corresponds to the respective computational node. The number of computational nodes is unlimited. This method is known as the block-splitting method or as the skip-ahead method.

Use this function when the number of elements to skip in a random stream is greater than 2 ⁶³ . Prior calls to the function represent the number of skipped elements with array of size n as shown below:

nskip [0]+ nskip [1]*2 ⁶⁴ + nskip [2]* 2 ¹²⁸ + … + nskip [n-1]*2 ^{(64*(n-1) )} ;

When the number of skipped elements is less than 2 ⁶³ you can use either vslSkipAheadtreamEx or vslSkipAheadStream . The following code illustrates how to initialize three independent streams using the vslSkipAheadStreamEx function:

!...
type(VSL_STREAM_STATE) ::stream1 type(VSL_STREAM_STATE) ::stream2 type(VSL_STREAM_STATE) ::stream3

! Creating the 1st stream
status = vslnewstream(stream1, VSL_BRNG_MRG32K3A, 174)

! To skip 2^64 elements in the random stream skipaheadstreamEx(nskip) function should
! be called with nskip represented as nskip = 2^64 = 0 + 1 * 2^64
integer(kind=8) nskip(2)
nskip(1) = 0
nskip(2) = 1

! Skipping ahead by 2^64 elements the 2nd stream
status = vslcopystream(stream2, stream1)
status = vslskipaheadstreamex (stream2, 2, nskip)

! Skipping ahead by 2^64 elements the 3rd stream
status = vslcopystream(stream3, stream2)
status = vslskipaheadstreamex (stream3, 2, nskip)

! Generating random numbers
!...

! Deleting the streams
status = vsldeletestream(stream1)
status = vsldeletestream(stream2)
status = vsldeletestream(stream3)
!...

Return Values

VSL_ERROR_OK , VSL_STATUS_OK: Indicates no error, execution is successful.
VSL_ERROR_NULL_PTR: stream is a NULL pointer.
VSL_RNG_ERROR_BAD_STREAM: stream is not a valid random stream.
VSL_RNG_ERROR_SKIPAHEADEX_UNSUPPORTED: BRNG does not support the advanced Skip-Ahead method.

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Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

vslSkipAheadStreamEx

Syntax

Include Files

Input Parameters

Description

Return Values